''When the 123 agreement is ratified by the US Congress, it will be the last expression of the legislature on the subject and will prevail over any earlier domestic law. Under Article VI(2) of the US Constitution, all treaties made or which shall be made under the authority of the United States shall be the supreme law of the land,'' he said, delivering the convocation address at the prestigious NALSAR University here.

The Hyde Act, which is a domestic law, cannot bind India and cannot interfere with the implementation of the 123 agreement. When ratified by the US Congress, it will be a bilateral treaty between two sovereign countries,'' he said.

He exhorted the new-graduates from NALSAR to help fellow citizens understand the legal aspects of the controversy.

Referring to Article 16(4) of the 123 agreement, he said, ''the agreement shall be implemented in good faith and in accordance with the principles of international law. Under customary international law as well as the Vienna Convention on Law of treaties, a party may not invoke provisions of its internal law as justification for its failure to perform a treaty.'' ''The 123 agreement has not come into force and even after it happens, India and the US will have to enter into further agreements to fulfil the objectives on industrial and commercial scale,'' he said, expressing disappointment on as to why the issues were not being raised and answered in a logical and rational manner.

''The agreement is only an enabling agreement and no more,'' he said, adding for operationalising it, both the countries had to complete pre-requirements, exchange diplomatic notes and agree upon a date on which it would come into force.

Mr Chidambaram said an agreement with the Internatonal Atomic Energy Agency (IAEA) and waiver from the Nuclear Suppliers Group(NSG) were indeed the pre-conditions. If these steps were completed, India would be able to enter into agreements for civil nuclear cooperation with other countries. India had entered into such agreements with the US (on July 20, 2007), France (on January 25,2008) and Russia (on February 11,2008).

Underscoring the importance of the deal, he said India had been denied access to nuclear reactors, fuel and technology, including dual use technology, since 1998 and as a result, the capacity utilisation of the 4120 MW nuclear plants had steadily declined from a high 90 per cent in 2001-02 to 54 per cent in 2007-08 due to nuclear isolation.

Hence, India wished to end the nuclear isolation and gain access to reactors, fuel and technology in return for the promise that certain civilian nuclear facilities -- to be determined by India autonomously -- would be segregated and placed under safeguards in a phased manner.

''Simultaneously, India will pursue its strategic nuclear programme without subjecting it to any safeguards or inspections,'' he said.

In order to access nuclear reactors, fuel and technology from the US and other supplier countries, India had agreed to enter into a safeguards agreement with the IAEA, of which India is a founder member, he said.

Only when these two steps were completed would India be able to seek and obtain cooperation in civil nuclear energy. Such cooperation had indeed been promised by France, Russia and the United States and there was a likelihood of such cooperation from other countries such as Australia, Canada, China and Japan, he added.